pyehouse

I’ve recently run into a situation where I needed to alter the mass for each part of a humanoid ragdoll in my Unity game. I had blindly accepted the default mass of ’20’ in the ragdoll wizard and Unity happily apportioned that 20 mass units across the various parts of the ragdoll. I’m not sure what unit of measure we should pretend Unity uses that makes sense to apply 20 of to represent an adult humanoid, but here we are.

Anyway, I wrote the following script to create an editor that would allow you to choose an object representing the highest level ancestor of your ragdoll, then choose a new mass. It then collects the current mass total, creates a ratio, then applies that ratio to each of the child rigidbodies.

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using UnityEngine;
using UnityEditor;
namespace Pyehouse.Editors
{
	public class RagdollMassAdjuster : EditorWindow
	{
		// Can be anything, make it smaller if you like...
		// just preventing divide by zero
		private const float SMALL_MASS_EPSILON = 0.00001f;
		private static bool TooSmall(float m)
		{
			return System.Math.Abs(m) < SMALL_MASS_EPSILON;
		}
		private static RagdollMassAdjuster editor;
		private static int width = 350;
		private static int height = 300;
		private static int x = 0;
		private static int y = 0;
		private bool noRigidbodies = false;
		private bool currentMassTooSmall = false;
		private float newMass = 20f;
		private GameObject ragdollParent;
		private void Awake()
		{
			ragdollParent = Selection.activeGameObject;
			Rigidbody[] rigidbodies = ragdollParent.GetComponentsInChildren<Rigidbody>();
			if (rigidbodies != null && rigidbodies.Length > 0)
			{
				float mass = 0f;
				foreach (Rigidbody rigidbody in rigidbodies)
				{
					mass += rigidbody.mass;
				}
				currentMassTooSmall = TooSmall(mass);
				newMass = mass;
				noRigidbodies = false;
			}
			else
			{
				newMass = 20f;
				noRigidbodies = true;
			}
		}
		[MenuItem("Window/Pyehouse/Ragdoll Mass Adjuster")]
		static void ShowEditor()
		{
			CenterWindow();
		}
		private static void CenterWindow()
		{
			editor = EditorWindow.GetWindow<RagdollMassAdjuster>();
			x = (Screen.currentResolution.width - width) / 2;
			y = (Screen.currentResolution.height - height) / 2;
			editor.position = new Rect(x, y, width, height);
			editor.maxSize = new Vector2(width, height);
			editor.minSize = editor.maxSize;
		}
		private void OnGUI()
		{
			if (currentMassTooSmall)
			{
				EditorGUILayout.HelpBox(string.Format("Current mass of selected ragdoll is too small: {0}", newMass), MessageType.Error);
			}
			else if (noRigidbodies)
			{
				EditorGUILayout.HelpBox("No rigidbodies present in selected GameObject or children.", MessageType.Error);
			}
			else
			{
				EditorStyles.label.wordWrap = true;
				EditorGUILayout.HelpBox("The new mass will be applied, maintaining the same per-object ratio as currently exists.", MessageType.Info);
				EditorGUILayout.HelpBox("So if your head is currently 3 out of a total 20 and you want a total mass of 100, your head will become 15.", MessageType.Info);
				newMass = EditorGUILayout.FloatField("New Mass for Ragdoll:", newMass);
				if (GUILayout.Button("Update Mass"))
				{
					UpdateMass(newMass);
				}
			}
		}
		private void UpdateMass(float toMass)
		{
			if (ragdollParent == null) return;
			Rigidbody[] rigidbodies = ragdollParent.GetComponentsInChildren<Rigidbody>();
			if (rigidbodies == null || rigidbodies.Length < 1)
			{
				Debug.LogErrorFormat("No rigidbodies found on selected object.");
				return;
			}
			float fromMass = 0f;
			foreach (Rigidbody rigidbody in rigidbodies)
			{
				fromMass += rigidbody.mass;
			}
			if (TooSmall(fromMass))
			{
				Debug.LogErrorFormat("Current mass too small: {0}", fromMass);
				return;
			}
			float ratio = toMass / fromMass;
			foreach (Rigidbody rigidbody in rigidbodies)
			{
				rigidbody.mass *= ratio;
				EditorUtility.SetDirty(rigidbody);
				EditorSceneManager.MarkSceneDirty(rigidbody.transform.gameObject.scene);
			}
		}
	}
}